A Boolean indicating whether to place the animation in the effects queue. If false, the animation will begin immediately. As of jQuery 1.7, the queue option can also accept a string, in which case the animation is added to the queue represented by that string. When a custom queue name is used the animation does not automatically start; you must call .dequeue("queuename") to start it.

A function to call once the animation is complete, called once per matched element.

The .slideDown() method animates the height of the matched elements. This causes lower parts of the page to slide down, making way for the revealed items.

Durations are given in milliseconds; higher values indicate slower animations, not faster ones. The strings 'fast' and 'slow' can be supplied to indicate durations of 200 and 600 milliseconds, respectively. If any other string is supplied, or if the duration parameter is omitted, the default duration of 400 milliseconds is used.

We can animate any element, such as a simple image:

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<divid="clickme">

Click here

</div>

<imgid="book"src="book.png"alt=""width="100"height="123">

With the element initially hidden, we can show it slowly:

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$( "#clickme" ).click(function() {

$( "#book" ).slideDown( "slow", function() {

// Animation complete.

});

});

Figure 1 - Illustration of the slideDown() effect

Easing

As of jQuery 1.4.3, an optional string naming an easing function may be used. Easing functions specify the speed at which the animation progresses at different points within the animation. The only easing implementations in the jQuery library are the default, called swing, and one that progresses at a constant pace, called linear. More easing functions are available with the use of plug-ins, most notably the jQuery UI suite.

Callback Function

If supplied, the callback is fired once the animation is complete. This can be useful for stringing different animations together in sequence. The callback is not sent any arguments, but this is set to the DOM element being animated. If multiple elements are animated, it is important to note that the callback is executed once per matched element, not once for the animation as a whole.

As of jQuery 1.6, the .promise() method can be used in conjunction with the deferred.done() method to execute a single callback for the animation as a whole when all matching elements have completed their animations ( See the example for .promise() ).

Additional Notes:

All jQuery effects, including .slideDown(), can be turned off globally by setting jQuery.fx.off = true, which effectively sets the duration to 0. For more information, see jQuery.fx.off.

If .slideDown() is called on an unordered list (<ul>) and its <li> elements have position (relative, absolute, or fixed), the effect may not work properly in IE6 through at least IE9 unless the <ul> has "layout." To remedy the problem, add the position: relative; and zoom: 1; CSS declarations to the ul.

Examples:

Animates all divs to slide down and show themselves over 600 milliseconds.

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<!doctype html>

<htmllang="en">

<head>

<metacharset="utf-8">

<title>slideDown demo</title>

<style>

div{

background:#de9a44;

margin:3px;

width:80px;

height:40px;

display: none;

float: left;

}

</style>

<scriptsrc="https://code.jquery.com/jquery-1.10.2.js"></script>

</head>

<body>

Click me!

<div></div>

<div></div>

<div></div>

<script>

$( document.body ).click(function() {

if ( $( "div:first" ).is( ":hidden" ) ) {

$( "div" ).slideDown( "slow" );

} else {

$( "div" ).hide();

}

});

</script>

</body>

</html>

Demo:

Animates all inputs to slide down, completing the animation within 1000 milliseconds. Once the animation is done, the input look is changed especially if it is the middle input which gets the focus.